Method and apparatus for replacing timing gears



I N VEN TOR 5 2004/5, 0. KJJI'EPJ Jan. 20, 1970 R KQSTERS ET AL METHOD AND APPARATUS FOR REPLACING TIMING GEARS Filed June 28, 1967 United States Patent 3,490,132 METHOD AND APPARATUS FOR REPLACING TIMING GEARS Rodney D. Kosters, 689 72nd St. SE., Grand Rapids, Mich. 49508; Lewis A. Hammond, 16192 Peach Ridge Road, Kent City, Mich. 49330; and Richard E.

Spaulding, P.O. Box 559, Waldport, Oreg. 97394 Filed June 28, 1967, Ser. No. 649,637 Int. Cl. B23p l9/04; B22d 19/10 US. Cl. 29-401 2 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND This invention relates to a method and apparatus for replacing timing gears on certain types of automotive engines and, more particularly, to such an apparatus and method whereby replacement may be effected without complete removal of the camshaft from the engine block.

In a number of modern types of automotive engines, rotational thrust is transmitted from the crankshaft to the camshaft via a system of two intermeshing gears located at the forward end of the engine block. One of these gears, commonly referred to in the art as the crankshaft gear, is affixed to an exposed extremity of the crankshaft and the other of these gears, commonly referred to as the timing gear, is affixed to the exposed end of the camshaft. As will be readily appreciated by those skilled in the art, the rotational displacement of the camshaft at any given moment must maintain a fixed relationship with respect to the rotational displacement of the crankshaft. This factor necessitates extremely accurate gear mesh between the two rotating components. If, for example, the timing gear should become worn so as to have some rotational slop with respect to the crankshaft gear, the engine will no longer function correctly and the timing gear, which is usually fabricated from softer metal than the crankshaft gear, must be replaced.

The replacement of the timing gear in engines of the types described has involved heretofore a complicated and time consuming task of removing the camshaft completely from the engine such that it may be placed in a press to force the new timing gear onto the normally exposed extremity thereof. Such removal necessitates prior removal of the radiator, grill, timing gear cover, valve cover, rocker arm assembly, the push rods, the engine side covers and all lifters. This process is necessitated by the undesirability of exerting any rearward thrust on the camshaft while it is in place in the engine. If, in fact, any such thrust is exerted on the camshaft, the bearing structure lCC which rotatably supports the rear extremity thereof will be ruined. For this reason, it is not possible to merely pound the new timing gear onto the exposed end of the shaft with a hammer or the like.

Once the camshaft has been removed from the engine and the new timing gear pressed in place thereon, the engine must be reassembled and properly adjusted. The replacement operation has required heretofore approximately 8 to 10 hours to complete. For example, it is customary in the auto industry to perform the replacement operation on an eight and one-half hour base price, thus, resulting in a rather expensive over-all operation. This charge, of course, is past ordinarily directly to the customer or the guaranteeing automobile manufacturer. Despite this fact, however, the particular mechanic or garage performing the service is tied up for a relatively lengthy period and, thus, cannot perform his ordinary servicing functions with regard to other types of automotive problems.

OBJECTS AND SPECIFICATION It is an object of this invention to provide a method and/ or apparatus for replacing the timing gear on engines of the type described which markedly reduces the amount of service time necessary for the procedure.

More particularly, it is an object of this invention to provide a method and/ or apparatus of the type described which will reduce the mechanics time for a reinstallation of the type described by a factor of approximately four and, thus, which will reduce markedly the expenses involved.

It is an object of this invention to provide a method and/or apparatus of the type described wherein timing gear replacement may be effected without removal of the camshaft from the engine and, yet, wherein no appreciable rearward thrust is exerted on the chamshaft which might damage its supporting bearings or otherwise impair its operative functions.

These as well as other objects of this invention will be readily understood by those skilled in the art with reference to the following specification and accompanying figures in which:

FIG. 1 is a fragmentary, front-elevational view of a typical engine block with the timing gear cover removed to expose the intermeshing timing and crankshaft gears;

FIG. 2 is a side-elevational view of the forward camshaft structure showing the drill jig and drill in exploded fashion;

FIG. 3 is an exploded perspective view indicating the manner in which the new timing gear is forced onto the exposed extremity of the camshaft; and

FIG. 4 is a perspective view of the gear-abutting bearing plate.

Briefly, this invention comprises a method of and/or apparatus for replacing a timing gear on an engine camshaft. After removal of the old timing gear, a generally longitudinal recess is bored in the exposed extremity of the camshaft and a threadedlug secured into the recess. The new timing gear is positoned over the lug and a bearing plate having a larger, nominal cross-sectional area than the shaft receiving aperture in the gear is secured to the exposed extremity of the lug and drawn toward the exposed extremity of the camshaft by means of the threaded lug to press the timing gear ontothe camshaft.

' Referring now to the figures, a preferred embodiment of this invention will be described in detail. FIG. 1 illustrates an engine block having a camshaft 11. Camshaft 11 has an exposed timing gear receiving extremity 12 upon which is press fitted a timing gear 13. Timing gear 13 comprises a conventional boss 14 having aflixed thereto a planar section 15 with a circular toothed periphery 16. The boss 14, and, thus, the entire timing gear 13 is keyed to the timing gear receiving extremity 12 of camshaft 11 as indicated at 17.

The crankshaft 18 has a conventional crankshaft gear 19 secured thereto in such a manner that it intermeshes with timing gear 13. The rotational position of the crankshaft at any particular moment is transmitted to the camshaft via the intermeshing gears 13 and 19' such that the engine valves and distributor function in correct chronological sequence during operation of the engine. In actual operation, of course, the timing gear 13 and crankshaft gear 19 are covered by a suitable pan or the like and usually ride behind the radiator and grill in the automobile.

As noted previously, a tendency exists for the periphcry .16 of the timing gear to wear in such a manner that some rotational slop exists between the crankshaft gear 19 and the timing gear 13. This slop, of course, permits the camshaft to get out of time with respect to the crankshaft and, thus, causes the engine to function improperly. When such slop has been found to exist, the timing gear must be replaced if the engine is to function properly thereafter.

Once this particular problem has been diagnosed, the grillwork, radiator and gear cover are removed from the automobile. Several satisfactory methods are well-known in the art for effecting removal of the old timing gear without necessitating the removal of the camshaft from the engine. It has been found, for example, that by drilling a pair of holes such as indicated by the reference numeral 20 in FIG. 1 on opposite sides of the shaft aperture adjacent the boss 14 and thereafter driving a pair of tapered plugs into the holes, the old timing gear may be removed with ease without fear of damaging the camshaft assembly. If, on the other hand, the particular timing gear in question has already been provided with apertures in its planar surface 15, it is often possible to utilize a conventional wheel puller to remove the worn gear.

Once removal of the worn gear has been effected, an aperture or recess is drilled into the forward extremity of the camshaft. Preferably, the recess is oriented generally longitudinally with respect to the camshaft such that its boundaries lie concentrically with respect to the gear receiving portion 12 of the camshaft. As shown in FIG. 2, the drilling operation may be effected conveniently by placing a jig having a cylindrical forward section 31 and a cylindrical butt section 32 over the exposed extremity of the camshaft 11. The forward section 31 of jig 30 has an inside diameter 33 adapted to be slidably, but positively, accommodated by the exposed extremity of the camshaft 11. The cylindrical butt section 32 has an inside diameter 34 which is just slightly larger than the particular drill to be utilized. The jig 30 is placed over the extremity of the crankshaft and the cap screw 35 turned to lock it in that .position. The drill 36 is then inserted through the end of the jig and into the metallic camshaft until a channel or recess of sufficient depth (approximately one-half to one inch) has been formed. Thereafter, the jig 30 is removed and the aperture or recess tapped to accommodate a threaded stud.

The jig 30 is fabricated such that the drill receiving channel 34 is symmetrically positioned with respect to the camshaft receiving portion 33 and, thus, the hole so formed will be in the center of the exposed extremity of the camshaft. The jig 30 may be fabricated, conveniently, from a piece of cylindrical metal stock in any conventional manner.

Once the aperture so drilled in the forward extremity of the camshaft has been tapped, a piece of threaded stock 41 is secured thereto by screwing it thereinto (see FIG. 3). The new timing gear 13 is inserted over the threaded stud 41 by passing the stud through the shaft receiving aperture in the boss 14'. A bearing or pressure plate 42 is placed over the lug 41 in such a manner that the new timing gear 13' lies between it and the exposed extremity of the camshaft and a nut threaded onto the exterior of the lug 4.1. As the nut 48 is rotated to draw the pressure plate 42 toward the camshaft extremity, the timing gear 13' is gradually forced onto the camshaft extremity. Of course, the key 17 must be positioned on the camshaft prior to forcing the gear thereonto.

The hearing or pressure plate 42 (see FIGS. 3 and 4) comprises a cylindrical bearing section 43 having an aperture 44 through the center thereof adapted to slidably receive the threaded lug 41. The bearing plate 42 is provided with a washer-like shoulder section 45 having a depth 46 equalling the desired overhang of the camshaft extremity from the boss 14 after complete insertion of the timing gear on the end of the camshaft. The washerlike shoulder 45 has an inside diameter 47 approximately equal to or slightly larger than the camshaft extremity to permit it to pass thereinto during the final pressing stages. At this point, of course, the shoulder pushes the timing gear onto the camshaft such that a portion of the camshaft extremity is thereafter exposed.

No over-all axial thrust is exerted on the camshaft during the installation procedure since the tension force is exerted directly between the camshaft and the gear being inserted thereof. The operation may be effected, therefore, without fear of damaging the camshaft supporting bearings or the push rod assemblies. After the installation has been completed, the threaded lug 41 is removed from the tapped hole in the camshaft extremity and the vehicle reassembled. The presence of the tapped hole or channel in camshaft extremity 12 does not interfere with proper functioning of the camshaft. This hole may be of sufficiently small dimension with respect to the camshaft diameter so as to not appreciably alter its structural characteristics.

Thus, it will be seen that this invention has provided a method and/or apparatus for installing a new timing gear in an engine which may be effected with both dispatch and efficiency, it no longer being necessary to dismantle the engine almost completely so that the new gear may be placed on the camshaft.

While a preferred embodiment of this invention has been illustrated in detail, it will be readily apparent to those skilled in the art that many other embodiments may be conceived and fabricated without departing from the spirit and scope of this specification and the accompanying drawings.

We claim:

I. A method of replacing a timing gear on an engine camshaft without removing said camshaft from the engine comprising the steps of:

removing the old timing gear;

boring a generally longitudinal recess in the exposed extremity of the camshaft;

securing a threaded lug into said recess;

positioning a new timing gear over said lug;

positioning a bearing plate over the exposed extremity of said lug, said bearing plate having a larger nominal cross section than the shaft receiving aperture in said gear; and

drawing said bearing plate toward the said exposed extremity of said camshaft by means of said threaded lug to press said timing gear onto said camshaft.

2. A method of replacing a timing gear on an engine camshaft Without removing the camshaft from the engine comprising the steps of:

removing the old timing gear;

securing an elongated lug to the exposed timing gear receiving extremity of said camshaft;

positioning the replacement timing gear over said lug;

positioning a bearing member over the extremity of said lug such that said timing gear lies between said bearing member and said extremity; and

drawing said bearing member toward the said exposed extremity of said camshaft by mechanical advantage means by tensioning said lug to press said timing gear onto said camshaft.

References Cited UNITED STATES PATENTS 2,840,399 6/1958 Harless et al. 287-53 3,141,689 7/1964 Rohde 287-53 3,181,902 5/1965 Aitken 28753 3,208,134 9/1965 Krewson 29401 3,230,616 1/1966 Janssen 29159.2 X

OTHER REFERENCES Maintenance Manual, revised, three, four, and six cylinder, Series 71 diesel engines, Detroit Diesel Engine Division, General Motors Corporation, reprinted October 1948, sec. 7, p. 5.

Diesel Engine Maintenance Manual, Model 6V71, GMC Truck & Coach Division, General Motor Corporation, March 1960, pp. 53-56.

JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner US. Cl. X.R. 

